KPNO 4 Meter Mayall - Basic Parameters and Facts

This page describes the current 4 Meter configuration

Location: 

Longitude: 111:35:59.6 W,  Latitude: 31:57:50.5 N,  Altitude: 2123.2m MSL

 

Basic Optical Data

Primary Mirror

Radius of curvature 21318.0 mm concave
Conic constant -1.09763
Mirror diameter 4011.6 mm (Drawing 2106-E1)
Bare mirror clear aperture diam 4002.6 mm
Central hole diam 1324 mm
Used clear aperture diam 3797 mm (Measured by Phil Massey)
Central obscuration diam 1651 mm (PF cage)
Central obscuration diam 1800 mm (DESI cage)
Light-collecting area 9.182 m²
Light-collecting area 8.658 m² (DESI)
PF Mosaic Focus Calibration 1.043 microns/unit

F/7.8 Secondary Mirror

Distance from primary 7492.0 mm
Radius of curvature 9643.0 mm convex
Conic constant -5.2951
Clear aperture diam 1191.6 mm (CHECK)
Secondary to RC focus 9306.2 mm
Instrument rotator to RC focus 152.4 mm
Effective focal length 31258.7 mm
Focus Calibration 0.991 microns/unit

F/15 Secondary Mirror

Distance from primary 8634.5 mm
Radius of curvature 5000.2 mm convex
Conic constant -3.09014
Clear aperture 742.7 mm
Secondary to SQIID focus 10895 mm
Instrument rotator to SQIID focus 598.7 mm
Effective focal length 57160.3 mm

Prime Focus (f/3.1) Corrector and ADC Prisms

Opto-Mechanical Assembly - 4 Meter Prime Focus Corrector

The 4-m prime focus corrector is described in Jacoby, Liang, Vaughnn, Reed, and Armandroff (1988 SPIE, 3355, 721).

Slew Time

Calculated slew and servo settling time for the 4-meter telescope with the new Mayall Active Primary Support (MAPS) implementation. Slew motion occurs in both HA and DEC simultaneously, so the time estimate should use the longer of the two motions.

South East Annex Position

The position of the telescope when at the South East Annex is:
Hour Angle = 3:44:40 E. and Declination = 31:36:00 S.

4MAPS - 4 Meter Active Primary System

4MAPS Manual (NOAO only)

Risley Prisms - Cass Focus

Risley Prisms Deployable
Clear Aperture 172 mm
Total Thickness 104 mm
Front Element to R-C Focus 931 mm
Clear Field f/7.8 45.3 mm = 298 arcsec

Telescope

Cassegrain Cage Mechanical Data

Component Weight(lb) Moment (in-lb)*
Instrument rotator 960 6720
Guider 640 11520
Allowable instrument 1350
Total load 2950 72570

* datum=back of primary mirror cell

additional weight information

Optical Layout Figure

Automatic Guider Bolt Pattern

Cassegrain Cage Clearances

Cassegrain Instrument Rotator

Cassegrain Guider Assembly

Dome

There are some old (and old-fashioned paper) enormous drawings of the dome and environment, but they are like ancient papyrus and very crowded with information.

 

Mayall HA Operation Limits

Declination

Lower Shutter Up
Airmass = 2.1*

Lower Shutter Down
Airmass = 3.0

+80 6:20 6:20
+70 6:20 6:20
+60 5:50 6:20
+50 5:40 6:20
+40 5:15 6:05
+30 4:50 5:35
+20 4:35 5:10
+10 4:15 4:50
0 3:45 4:20
-10 3:10 4:00
-20 2:25 3:15
-30 0:30 2:20
-40 --- ---

* Note: The Airmass=2.1 limit was determined for Mosaic3. For DESI, with its 1.5 degree field, it's advised to point only to targets of airmass < 2.0 with the lower shutter raised.